Voltage-control system



June 17, 1930. K. KURDA VOLTAGE CONTROL SYSTEM Filed July 11, 1928 INVENTOR A or/ MFG 0.

ATi'QRNEY Patented June 17, 1930 UNITED STATES PATENT OFFICE KARL KURDA, F NUREMBERG, GERMANY, ASSIGNOR T0 WESTINGHOUSE ELECTRIC 8b MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA VOLTAGE-CONTROL SYSTEM Application filed July 11, 1928, Serial No. 291,862, and in, Germany April 8, 1927.

My invention relates to voltage-control systems and has particular reference to Such systems wherein voltage regulation under load may be effected.

In accordance with my invention, there is utilized a regulator switch that comprises a plurality of contactors that may be connected to carry no current and whereof the contacts are connected in pairs to the tapping places of the regulable winding.

Further in accordance with my invention, both of the parallel-circuit selectors may be connected to the contacts of a load switch through which the selectors may be deenergized at any time.

The load switch and the selector circuit contacts are coupled together by gearing operating in such manner that, during voltage regulation at any time, the first selector circuit is made currentless and then advanced one step. Both selector circuits are then connected in parallel and the second selector circuit is made currentless and then moved to the contact position of the first selector circuit. All of these movements are positively operated simultaneously and finally both selector circuits are connected in parallel.

In order to diminish the balancing current that is created during the bridging over of the selector circuits temporarily connected to different voltage taps, I provide ourrent-limiting means inserted between the selector circuits and the contacts of the load switch. 1

My invention resides in the system, mechanism and features of construction of the character hereinafter described and claimed.

For an understanding of my invention and for an illustration of some of the forms my system or mechanism may take, reference is to be had to the accompanying drawing, in which: I

Figure 1 is a schematic View of a transformer tap changing system constructed in accordance with my invention;

Fig. 2 is a view similar to Fig. 1 of a modification of my invention;

Fig. 3 is a view similar to Fig. 1 of a further modification of my invention;

Fig. 4 is a view in side elevation and par tially in section of my manner of assembling the apparatus illustrated in the other figures; and

Fig. 5 is a plan view showing how the regulator switch is associated with the Maltese gear.

Figure 1 illustrates diagrammatically the connections of a tap-changing-transformer system constructed in accordance with my invention. The winding 1 of a main transformer is subdivided by taps 2, 3 and 4 into substantially equal groups. To the taps 2, 3 and 1 are connected in pairs the contacts 2a, 3a and 4a and 2b, and 4?), respectively, of the voltage selector circuit contacts which latter are represented for simplicity by slide contacts 5 and 6. The voltage selector contact 5 is connected through a winding 7 to a contact member 8 and the voltage selector contact 6 is connected through a winding 9 to a contact member 10 of a load switch 11. The windlngs 7 and 9 are arranged, to ether with a winding 12, on an iron core 12 The windings 7 and 9 are so designed and connected to the load circuit, that the magnetic fluxes produced by the currents in the said two-windings neutralize each other when the load current is uniformly divided between the two windings. When the fluxes from the primary windings 7 and 9 neutralize each other, which is the normal operating condition, no voltage will be induced in the winding 12.

The terminals of the winding 12 are bridged by a resistor 13 serving to limit the balancing current that flows from one selector circuit through the load switch to the other selector circuit when the selector contacts are connected at different tapping positions in the intermediate positions of the regulating apparatus. The resistor 13 is of a resistance of such magnitude that the balancing current does not exceed the amount of one-half the normal load current.

The switch operates in the following manner: If the voltage is to be lowered by one step, the contact 8 is first made ourrentless by rotating the load switch 11.

' switc The step selector 5 is moved from the contact 4a to the contact 3a, then by further rotation of the load switch 11in the same direction, the contact 8 is connected to the contact 10 and thereupon the contact 10 is made currentless and the step selector moves from the contact 4?) to the contact 312 and finall by further rotation of the load b in the same direction, contacts 8 and 10 are again bridged and the normal operating conditions produced.

For raising the voltage, the operation is in the opposite direction. The contacts of the step selectors may be conveniently arranged circularly and the step selectors are then made in the form of rotary switches. They may be coupled by gearing to the load switch 11 for posltively producing the above described operations in correct sequence and time intervals.

Another arrangement according to my incation, the load switch 11 has four contacts 8a, 8?), 10a and 10b. The contacts 8a, 8b are short-circuited with each other, and the contacts 10a, 10?) are bridged by a resistor 14 that preferably corresponds to the quotient of step voltage and normal load current. Otherwise, the arrangement is similar to that of Fig. 1. Corresponding elements are denoted by the same reference numerals. The mode of operation is substantially similar, except that the load switch 11 interposes the resistor 14 when the step selectors are connected to different voltage steps.

In order to increase the range of-rcgulation of the transformer without requiring a fine stage subdivision of the whole transformer winding, there is mounted on the iron core, in addition to the fine sta e subdivided winding, also a coarsely subdivided winding, the magnitude of the steps of which is equal to the sum of the voltage steps on the finel subdivided winding. Furthermore, additional step selectors are provided for the tapping places of the coarse stage winding, which permits a connection of the fine stage winding with the separate stages of the coarse stage winding.

Such a construction is shown in Fig. 3. The upper part of the figure corresponds essentially to Fig. 2, but there is provided an idle contact 15 or 16 on the two step selectors 5, 6, which idle contacts are connected with a step selector 17 for the coarse step subdivided winding 18. The second step selector 19 is connected with the end 20 of the fine stage winding.

For example, if the voltage is to be lowered, the separate stages of the fine stage winding can be operated stepwise in the above described manner until the step selector 5 arrives on the contact 21 and the step selector 6 on the contact 22. Thereupon, the two step selectors are placed on vention is shown in Fig. 2. In this modificontacts 15, 16 in succession, having been made currentless by the load switch 11, as previously. In this position, the fine stage winding is disconnected from the circuit of the load current. This end 20 is now switched over by turning the step selector 19, from the contact 23a to the next lower contact 24a. The beginning 25 of the fine stage winding has the same potential as the idle contacts 15, and 16, that is, as the beginning 26 of the coarse stage winding 18. Therefore, the step selectors 5, 6, can be "moved 011 to the contact steps connected with the winding end 25. This movement takes place successively in the same manner as described previously, the actuated step selectors being made currentless by the load switch 11. In the course of the followin switch movements also the step selector 1 is advanced from the contact 236 to the contact 24b.

The step selectors 17, 19 for the coarse stage winding may be coupled with the gearing of the step selectors 5, 6 and with the load switch 11 in such a manner that the above-mentioned operations take place positively in the correct sequence and at the correct time.

An increase of the range of regulation of the transformer can also be obtained by using a blind contact in the ste selectors and by switching the step subdivided winding oppositely to the other winding of the transformer, in one case and in series in the other case.

A construction of theswitch gearing is shown in Fig. 4, for a regulating transformer according to the system illustrated in Fig. 1. The load switch comprises a movable contact member 11 and two stationary contact members 8 and 10. Both the arts of the load switch are mounted on insulators 11a and 8a and 10a. 5 denotes a step selector in the form of a rotary switch, and 6 the second step selector. The contact blades 27, 28 of the step selectors are insulatedly mounted on the hubs 29, 80. The current collection from the blades is effected by slip rings 31, 32, the slip ring 31 engaging the blade 27 and the slip ring 32 engaging the blade 28. The current collection from the slip rings takes place by means of brushes 33, 34.

The contacts connected to the tapping places are insulatedly arranged in a circle around the step selectors 5, 6. In the drawing, only one pair of contacts 35, 36, 37, 38 for each is shown.

The hub of the step selector 6 is fixed on the shaft 39 on which there is keyed a Maltese gear 40. The hub of the step selector 5 is fixed to a hollow spindle 41 on which is mounted a second Maltese gear 42. The Maltese gears are alternately actuated by the driving pins 44, 45, arranged on opposite sides, and at an angle of 180 to each other on a disc 43, and at which rotation of the disc 43 they are advanced one step. The disc 43 is driven through bevel gearing 46 from a shaft extending out of the container (not shown). The movable member ll of the load switch is also coupled to the disc 43. The angle between two neighboring teeth of the Maltese gearing is equal to the angle between the tap contacts.

While I have shown and described my invention in connection with knife switches and the like, it will be readily appreciated by those skilled in the art that my invention may be made equally operable by means of solenoid contactors or circuit breakers. I desire that all such modifications and changes shall be included within the spirit and scope of the appended claims.

I claim as my invention:

1. A regulator switch for tap-changingunder-load equipment comprising, parallel circuits, movable contact members associated with the terminals of said circuits, a main transformer winding divided into a plurality of sections, said contact members coopcrating with the ends of said sections, and means including a rotary switch for de energizing said contact members during movement and a Maltese gear for control ling said switch, return-current contacts mounted on said rotary switch, two coils wound on the same iron core, a terminal of each of said coils being connected to one of said return-current contacts, the other terminal of each of said coils being connected to one of said movable contact members, a third winding inductively associated with said coils, and an ohmic resistance in circuit relation with said third winding.

2. The combination with a main transformer winding comprising a lurality of sections, of an auxiliary trans ormer hav ing a plurality of primary windings and a secondary winding, means associated with the secondary winding of said auxiliary transformer for consuming current, and means for associating said primary windings with one of said winding sections.

3. In tap-changing-under-load apparatus, the combination with conductors tempora rily connected to different taps whereby an electrical circuit is established, of means for limiting current tending to traverse said circuit comprising a transformer and a resistor coacting therewith.

4. The combination with an electric circuit comprising a coil having a. plurality of turns, of means for changing the number of said turns of said coil in said circuit while energy is traversing the latter, said means including a transformer having a plurality of primary windings and a secondary winding in electrical circuit relation with a resistor, and means normally connecting said primary windings in parallel-circuit relation with each other and in series-circuit relation with said coil for disconnectin one terminal of one of said primary windings, and means for changing the other terminal thereof to a different position on said coil.

5. In tap-changing-under-load apparatus, the combination with coil having a plurality of taps, of means for limiting the balancing current created during the bridging of conductors temporarily connected to different voltage taps of said coil. comprising a transformer having a plurality of primary windings, each in circuit relation with one of said conductors, and a secondary winding close circuited through a current-consuming element.

In testimony whereof, I have hereunto subscribed my name this 1st day of June, 1928, at Nuremberg, Germany.

KARL KURDA. 

